Thank you AJ. It looks like I was misled by HobbyPeople who told me the 7.2v would perform better than the 6v. I have the specs and it looks like the opposite is true although I don't understand why a lower voltage motor would outperform a higher voltage.

Thing is with the Neon, the remaining batteries all measure 1.5v which tells me they are not drained. There still could be a short causing the low power to activate and for whatever reason stressing the batteries. What causes a battery to leak, too much v? Just a short somewhere?